Field of the Invention
The disclosure generally relates to an antenna system, and more particularly to an omnidirectional antenna system with multiple polarization directions.
Description of the Related Art
With the progress of mobile communication technology, mobile devices, such as portable computers, mobile phones, multimedia players, and other hybrid functional mobile devices, have become more common. To satisfy consumer demand, mobile devices can usually perform wireless communication functions. Some functions cover a large wireless communication area; for example, mobile phones using 2G, 3G, and LTE (Long Term Evolution) systems and using frequency bands of 700 MHz, 850 MHz, 900 MHz, 1800 MHz, 1900 MHz, 2100 MHz, 2300 MHz, and 2500 MHz. Some functions cover a small wireless communication area; for example, mobile phones using Wi-Fi and Bluetooth systems and using frequency bands of 2.4 GHz, 5.2 GHz, and 5.8 GHz.
Wireless access points are indispensable elements for mobile devices in the room to connect to the Internet at a high speed. However, since the indoor environment has serious signal reflection and multipath fading, wireless access points should process signals in a variety of polarization directions and from a variety of transmission directions simultaneously. Accordingly, it becomes a critical challenge for antenna designers to design an omnidirectional antenna with multiple polarization directions in the limited space of wireless access points.